EnerVest Ltd. has a little bit more elbow room. The oil and gas firm has expanded its Houston headquarters by 36,721 square feet while renewing its headquarters lease for a total of 117,316 square feet in downtown’s First City Tower at 1001 Fannin.

The lease brings the tower to 95 percent occupancy.

According to EnerVest president and chief operating officer John Walker, the tower’s core downtown location and amenities made it the firm’s first choice for its headquarters. EnerVest was represented by Tim Relyea of Cushman & Wakefield, Houston, while landlord FC Tower Property Partners L.P. was represented by Chip Colvill and Michael Anderson of Colvill Office Properties.

EnerVest operates more than 18,000 wells in 12 states and plans to close the largest institutional equity fund in its 18-year history, the $1.5 billion EnerVest Energy Institutional Fund XII, this fall.